The Beatles were the first "band" as we know it -- not the first band of course, but they were the first rock band that made it really big and famous, therefore they are the model for all future rock bands, in terms of nearly everything bandsy you can think of. No, it wasn't the Beatles that pimped swordfish. That is why I said "nearly".

The most important thing is of course, the music. The Beatles did it all.

They did the jingle-jangle thing, they did the early RnR Chuck Berry thing, they did the Bob Dylan thing, they did the blues-rock thing, they did the heavy metal thing, they did the out-there space out thing, they did the gorgeous ballad thing, they experimented with countless styles, from calypso to South Indian carnatic music, and most of it was in a rock and roll context, all sounding like the Beatles, and it was musically as sophisticated as can be.

Their musical progression in a few short years was astounding. They did the first "concept album", they were the first to exploit studio experimentation (it didn't hurt that they had a secret weapon called "George Martin")... they were apparently the first to purposely incorporate feedback into a song, the first to use backwards guitar solos, they incorporated all different types of instruments in their rock and roll music, they made rock and roll respectable as a legitimate form of serious (and not-so-serious) music, they were lyrically sophisticated, they were funny, clever, witty, socially conscious, and talented beyond measure. And -- their music was great.

All that said, it is very possible to not really like them that much, but at least now you know why myself and others consider them so great.